The invention relates to a circuit arrangement for an automated press system.
A known circuit arrangement for automated press control is described in U.S. Pat. No. 3,668,498. The circuit arrangement set forth there is provided with a numeric control system based on a digital incremental design. In this arrangement a pulse generator coupled to the press drive produces pulses, the number of which is proportional to the travel of a press ram at the crank circle. These pulses are fed to an evaluation circuit, and have an indirect effect that the actuators, and thus the automation system, follow an operating characteristic, which is predetermined by preprogrammable set points. For example, the operation can be controlled through positioning control circuits, such as speed/position control loops. The points which must be approached individually are set as counters which are fed with the pulses from the pulse generator. Furthermore, a matrix circuit is used to determine check points which can only be passed by the automation system when the press ram has reached a certain position, as established by the crank circle.
The operation described above is accomplished by comparison devices which are components of the evaluation circuit, in that the positioning control circuits are actuated only when the system moves up to the set points and the new data for the next set point can be read out. This circuit arrangement presupposes continuous press operation, whereas the automation system is run in start/stop mode.
This state-of-the-art circuit arrangement is characterized by high component expenditure, extensive programming, which essentially must be done manually, and the imperfect attempt to reproduce a synchronized press line with mechanically firmly-coupled automation systems such as that described in U.S. Pat. Nos. 3,199,439 and 3,199,443. The deficiencies of this arrangement are that the limited number of set and check points which it permits and the associated operating characteristic which can be changed within the limits. The limitation in the number of set and check points is determined by the number of counters in the evaluation circuit, or, in other words, by the amount of circuitry involved. In addition, operational reliability is adversely affected by the possibility that pulses from the pulse generator can get lost during transmission to the evaluation circuit, or that additional noise pulses can be transmitted, resulting in a wrong position allocation for the press ram. This also results in shortcomings in producing synchronous conditions between the press and the automation system.